Gradual change of pixel-resolution in oled display

ABSTRACT

An apparatus is described that includes an organic light emitting diode (OLED) display and a sensor. The OLED display includes a first area having a first pixel density, a second area having a second pixel density, and a third area having a third pixel density. The second area is arranged between the first area and the third area. The first pixel density is lower than the second pixel density. The second pixel density is lower than the third pixel density. The sensor is arranged to receive electromagnetic radiation transmitted through the first area of the OLED display.

TECHNICAL FIELD

The subject matter described herein relates to organic light emittingdiode (OLED) displays, and more specifically to pixel arrangements inOLED displays.

BACKGROUND

In general, organic light emitting diode (OLED) displays are emissiveflat panel displays featuring an array of pixels, each of which includesat least one OLED. During operation, a pixel circuit delivers electriccurrent to the OLED, causing it to emit light. Pixels in full color OLEDdisplays often include multiple sub-pixels, each emitting light of adifferent color. The sub-pixels are sufficiently small andclosely-spaced such that a viewer perceives the multi-colored emissionto emanate from a single point having a color corresponding to thecombined spectral emissions of the sub-pixels.

SUMMARY

In some devices, such as smartphones, it is desirable to includefront-facing sensors, i.e., sensors that face in the same direction asthe device's display. Traditionally, such sensors (e.g., cameras, facialrecognition sensors) have been housed in the display's bezel. However,it can be desirable to minimize the size of the display's bezel. In somecases, such as where the bezel is narrow, the front-facing sensors arepositioned behind the display and detect light that is transmittedthrough the display.

In certain cases, the display can include a region with lower pixeldensity above the front-facing sensor. This can facilitate increasedtransmission of light through the display to the sensor, therebyimproving the quality of any signal detected by the sensor. In suchcases, the display can include adjacent areas having different pixeldensities, and therefore different resolutions.

When an organic light emitting diode (OLED) display has two adjacentareas with significantly different resolutions of pixels in those areas,the image rendered on the OLED display can have an undesirably sharpcontrast in image quality along the boundary of those two areas. Forexample, FIGS. 1A and 1B illustrate an OLED display 102 having a firstarea 104 with a pixel-resolution of 222 pixels per inch, and a secondarea 106 with a pixel-resolution of 444 pixels per inch. As theresolutions of 222 pixels per inch and 444 pixels per inch aresignificantly apart, the image rendered on the OLED display 102 has anundesirably sharp contrast in image quality along the boundary 108 ofthose two areas 104 and 106.

Organic light emitting diode (OLED) displays are described that have agradual change of resolution of pixels. Such a resolution gradient canavoid an undesirable sharp contrast in image quality that occurs whenthere is a significantly large change in resolution of the pixels inadjacent areas.

In one aspect, an apparatus is described that includes an organic lightemitting diode (OLED) display and a sensor. The OLED display includes afirst area having a first pixel density, a second area having a secondpixel density, and a third area having a third pixel density. The secondarea is arranged between the first area and the third area. The firstpixel density is lower than the second pixel density. The second pixeldensity is lower than the third pixel density. The sensor is arranged toreceive electromagnetic radiation transmitted through the first area ofthe OLED display.

In some variations, one or more of the following can be additionallyimplemented either individually or in any feasible combination. The OLEDdisplay further includes a fourth area between the second area and thethird area. The fourth area has a pixel density between the second pixeldensity and the third pixel density. The apparatus further includes adisplay driver module programmed to display images in the second area atthe second pixel density lower than a physical pixel density in thesecond area. The physical pixel density in the second area and aphysical pixel density in the third area are the same. The physicalpixel density in the third area and the third pixel density are thesame.

Pixels in the first area are arranged in pixel clusters in a firstpattern, and pixels in the second area are arranged in pixel clusters ina second pattern that is different from the first pattern. The firstpattern is a quarter pattern. The second pattern is a diamond pattern ora mosaic pattern. The second area surrounds the first area. The thirdarea surrounds the second area. The first area is located at an edge ofthe display. The first area is 10% or less of a total area of the OLEDdisplay. The third area is 80% or more of a total area of the OLEDdisplay. The first pixel density is 250 pixels per inch or less. Thethird pixel density is 400 pixels per inch or more. The sensor is acamera. The apparatus is a smartphone.

The implementations discussed herein are advantageous. For example, thegradual change in resolution of pixels in the OLED display avoidsundesirably sharp contrasts in image quality, thereby making thebrightness of the image substantially uniform. Such OLED displays canalso facilitate operation of sensors placed behind the display byproviding a low pixel density area through which light can propagate tothe sensor.

The details of one or more implementations are set forth below. Otherfeatures and advantages of the subject matter will be apparent from thedetailed description, the accompanying drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B illustrate an OLED display with undesirably sharpcontrast in image quality when two adjacent areas of the OLED displayhave significantly differing pixel-resolutions.

FIG. 2 illustrates another OLED display where adjacent areas havegradually differing pixel-resolutions.

FIG. 3 illustrates multiple pixel-clusters within an OLED display.

FIGS. 4A-4I illustrates examples of pixel-clusters with correspondingsub-pixels.

FIG. 5 is a table that illustrates examples of various patterns in whichthe pixel-clusters can be arranged.

FIG. 6 illustrates the pixel-clusters in different areas of the OLEDdisplay.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 2 illustrates an example organic light emitting diode (OLED)display 202 of a computing device 203 with four areas of differing pixeldensity—a first area 204, a second area 206, a third area 208, and afourth area 210. Front-facing sensors 212 are located behind display 202in first area 204. The pixels in each area 204, 206, 208 and 210 of theOLED display 202 are arranged in pixel-clusters such as those describedbelow with reference to FIG. 3. A display driver module 220 (e.g.,including a processor, such as a GPU, and/or other appropriateintegrated circuit devices), housed within computing device 203,controls the operation of the display 202 by processing image data andgenerating appropriate drive signals for activating pixels in thedisplay to present images.

Generally, each pixel-cluster has one or more pixels, each of which caninclude two or more sub-pixels (e.g., three sub-pixels or foursub-pixels). Examples of pixel-clusters with corresponding pixels andsub-pixels are described below by FIGS. 4A-4I. The pixel-clusters can bearranged according to various patterns, depending on desiredtransmissivity and image quality, as explained below by FIG. 5. Theresolution of the pixels (which can also be referred to aspixel-resolution or density of pixels) can gradually change (e.g.,change in multiple small steps rather than one single step) from thefirst area 204 (which has the lowest resolution of pixels) to the fourtharea 210 (which has the highest resolution of pixels), as describedbelow by FIG. 6. This gradual resolution change can be implemented by aphysical layout in a display panel, and/or by digital image contentgenerated by software in the physically same resolution region each ofthe areas of the display.

The presence of three or more areas (e.g., four areas as shown in FIG.2) and the gradual change in resolution of pixels (as shown in FIG. 6)in those areas can reduce (e.g., obviate) the visual discontinuityperceived by a viewer where the image quality experiences a sharpdiscontinuity along the boundary of those two areas as described by FIG.1.

Generally, pixel-resolution can be measured in pixels per inch andtypically depends on the size of the display, its intended use (e.g.,how far from the display the intended viewing distance is), andmanufacturing constraints, for example. Displays with small formfactors, such as those used in mobile devices intended for closeviewing, can include areas with high pixel densities, such as greaterthan 300 pixels per inch (e.g., 400 pixels per inch or more, 500 pixelsper inch or more) for example. The lowest pixel density of the displaycan be determined based on the transmittance of light through the lowpixel density area needed for satisfactory operation of the front-facingsensors. In some embodiments, the lowest pixel density can be in therange of 200 pixels per inch or less (e.g., 180 pixels per inch or less,150 pixels per inch or less, 120 pixels per inch or less, 100 pixels perinch or less, 80 pixels per inch or less).

In some examples, the pixel-resolution in the first area 204 can bebetween 125 pixels per inch and 175 pixels per inch, thepixel-resolution in the second area 206 can be between 200 pixels perinch and 250 pixels per inch, the pixel-resolution in the third area 208can be between 275 pixels per inch and 375 pixels per inch, and thepixel-resolution in the fourth area 210 can be between 400 pixels perinch and 475 pixels per inch. In one specific example, thepixel-resolution in the first area 204 can be 157 pixels per inch, thepixel-resolution in the second area 206 can be 222 pixels per inch, thepixel-resolution in the third area 208 can be 313 pixels per inch, andthe pixel-resolution in the fourth area 210 can be 444 pixels per inch.These pixel-resolution values are merely exemplary, and any othergradually changing values can be used for different areas.

Additionally, the number of areas with gradually changingpixel-resolutions is shown here as four, which is merely exemplarynumber. In other implementations, for example, there can be any numberof areas with gradually changing pixel-resolutions, such as three, five,six, seven, eight, nine, ten, eleven, twelve, or so on.

Moreover, while a particular arrangement of differing pixel densityareas is shown in FIG. 2, more generally, the size and location of theseareas can vary as appropriate. Generally, the lowest pixel density area(i.e., area 204 in FIG. 2) is located over the front-facing sensors andshould be sufficiently large to provide adequate light transmissivity ofelectromagnetic radiation through the display to and from the sensors.Accordingly, in some embodiments, the low pixel density area can besituated at an edge of the display, e.g., at the top edge. Typically,the low pixel density area occupies a small amount of the total area ofthe display (e.g., 10% or less, 5% or less, 2% or less).

Generally, the highest pixel density area (i.e., area 210 in FIG. 2)should occupy the majority of the display, providing the highest imagequality and therefore best user experience. In some embodiments, thehighest pixel density area can be 80% or more (e.g., 90% or more, 95% ormore) of the total display area. Intermediate pixel density areas (i.e.,areas 206 and 208 in FIG. 2) are generally arranged between the lowestpixel density area and the highest pixel density area. Typically, theyare sufficiently large to provide a gradual transition in pixel densityfrom the low pixel density area to the high pixel density area, asperceived by the user.

In general, the geometry of each pixel in different areas of the displaycan be the same or can be different. For example, the size and shape ofthe OLED for each same-colored sub-pixel in each of the areas (e.g.,areas 204, 206, 208 and 210 in FIG. 2) can be the same or substantiallysimilar. Identical sizes of such OLEDs in various areas means that withthe gradual increase in pixel density (as measured in pixels per inch)between areas, there is a corresponding gradual decrease in space, perinch of display, between each pixel that does not emit light. Generally,area 204 that has the most amount of space between each OLED has thehighest light transmissivity for passing through the OLED display. Incontrast, area 210 that has the highest pixel density correspondinglyhas the least amount of space between OLEDs and therefore has the lowestlight transmissivity through the OLED display 202.

However, the trade off for having a low pixel density in area 204compared to area 210 is that the quality of a displayed image can bepoorer in area 204 compared to area 210.

To ensure that the change in pixel-resolutions is gradual, a differencebetween pixel-resolutions of adjacent areas can have a correspondingupper threshold value. For example, the difference between apixel-resolution of the second area 206 and a pixel-resolution of thefirst area 204 can be less than a first threshold value. A differencebetween a pixel-resolution of the third area 208 and a pixel-resolutionof the second area 206 can be less than a second threshold value. Adifference between a pixel-resolution of the fourth area 210 and apixel-resolution of the third area 208 can be less than a thirdthreshold value. In one example, the first threshold value can be 75pixels per inch, the second threshold value can be 90 pixels per inch,and the third threshold value can be 135 pixels per inch. These valuesof thresholds are merely exemplary, and in alternate implementationseach of the first threshold, the second threshold and the thirdthreshold can have any other values.

Generally, the variation in pixel density between adjacent areas ofdifferent pixel density can vary depending on the maximum and minimumpixel densities of the display, and the visual impact of the variationfrom region to region (e.g., determined empirically). For example, thechange in pixel density between adjacent areas can be in a range fromabout 20 pixels per inch to about 150 pixels per inch (e.g., about 30pixels per inch or more, about 40 pixels per inch or more, about 50pixels per inch or more, such as about 130 pixels per inch or less, 100pixels per inch or less, 80 pixels per inch or less).

As noted above, the physical location and dimension (i.e., physicalspace) of low pixel density area 210 corresponds to the location anddimension of sensors 212 in the computing device 203.

The sensors can include an image sensor (e.g., a camera), a proximitysensor, an ambient light sensor, an accelerometer, a gyrometer, amagnetometer, a fingerprint sensor, a barometer, a Hall effect sensor, afacial recognition sensor, any other one or more sensors, and/or anycombination thereof. At least one sensor 212 can include a transmitter214 and a receiver 216.

The OLED display can be driven with an active matrix display scheme, andthe OLED display can be referred to as an active matrix organic lightemitting diode (AMOLED) display. The active matrix display scheme can beadvantageous over a passive matrix display scheme in a passive matrixorganic light emitting diode (PMOLED) display, as AMOLED displays canprovide higher refresh rates than PMOLED displays, and consumesignificantly less power than PMOLED displays.

The computing device 203 can be a mobile device, such as a phone, atablet computer, a phablet computer, a laptop computer, a wearabledevice such as a smartwatch, a digital camera, any other one or moremobile device, and/or the like. In alternate implementations, the device100 can be any other computing device such as a desktop computer, akiosk computer, a television, and/or any other one or more computingdevices that are configured to output visual data.

In general, pixels in display 202 can be grouped together in clusters.FIG. 3, for example, illustrates pixel clusters 302, each of whichincludes one or more pixels of the OLED display 202. Each pixel caninclude two or more sub-pixels (e.g., red, green and blue sub-pixels).Examples of pixel clusters 302 with corresponding pixels and sub-pixelsare further described with reference to FIGS. 4A-4I. In certainimplementations, each area 204, 206, 208 and 210 of the OLED display 202includes pixel clusters 302 that have the same number and arrangement ofpixels. However, the spacing between neighboring pixel clusters,indicated by arrows 304, varies depending on the area of the display thepixel clusters are in. The varied spacing between pixel clusters resultsin different pixel densities within each area. In some embodiments,different areas of the display can have pixel clusters with differentpixel arrangements.

In embodiments where the physical pixel density varies between differentareas, the gaps between neighboring pixel clusters is set duringfabrication of the display panel. In an additional or alternateimplementation, the gaps can be varied in software using imageprocessing. The pixel clusters 302 can be arranged according to aparticular pattern based on desired transmissivity and image quality, asexplained below with reference to FIG. 5.

FIGS. 4A-4I illustrates various example pixel arrangements 402, 404,406, 408, 410, 412, 414, 416, and 418 for pixel clusters 302. Each ofthe pixel clusters 402, 404, 406 and 408 includes a single pixelcomposed of three sub-pixels having differing arrangements. In eachcase, the pixel cluster is square and the sub-pixels are rectangular.More specifically, the pixel cluster 402 includes a single pixel 402 p,the pixel cluster 404 has a single pixel 404 p, the pixel cluster 406has a single pixel 406 p, and the pixel cluster 410 has a single pixel410 p. Each of the pixels 402 p, 404 p, 406 p and 408 p includes threesub-pixels—a red sub-pixel 302 r 1, a green sub-pixel 302 g 1, and ablue sub-pixel 302 b 1. The edges of pixel clusters 402 and 404 arerotated 45 degrees with respect to the edges of the display, while theedges of pixel clusters 406 and 408 are parallel with the edges of thedisplay.

Each of the pixel clusters 410, 412 and 414 includes two rectangularpixels, each with two square sub-pixels. Particularly, the pixel cluster410 includes pixels 410 p 1 and 410 p 2, the pixel cluster 412 includespixels 412 p 1 and 412 p 2, and the pixel cluster 414 includes pixels414 p 1 and 414 p 2. Each of the pixels 410 p 1, 412 p 1 and 414 p 1includes two sub-pixels 302 r 2 and 302 g 2. Each of the pixels 410 p 2,412 p 2 and 414 p 2 includes two sub-pixels 302 b 2 and 302 g 2.

Pixel cluster 416 is a rectangular pixel cluster that includes twosquare pixels 416 p 1 and 416 p 2. Pixel 416 p 1 includes a redsub-pixel 302 r 1 and a green sub-pixel 302 g 1. Both sub-pixels aresquare and rotated 45 degrees with respect to the pixel square.Similarly, pixel 416 p 2 includes a blue sub-pixel 302 b 2 and a greensub-pixel 302 g 2, with similar orientations. The green sub-pixels aresmaller in area than the red and blue sub-pixels.

Pixel cluster 418 is a square pixel cluster composed of four squarepixels 418 p 1, 418 p 2, 418 p 3, and 418 p 4. Pixels 418 p 1 and 418 p4 each include a red sub-pixel 302 r 1 and a green sub-pixel 302 g 1.Both sub-pixels are square and rotated 45 degrees with respect to thepixel square. Similarly, pixels 418 p 2 and 418 p 3 each include a bluesub-pixel 302 b 2 and a green sub-pixel 302 g 2, with similarorientations. The green sub-pixels are smaller in area than the red andblue sub-pixels.

While each pixel shown in FIGS. 4A-4I have either two or threesub-pixels, in alternate implementations pixels may have other numbers(e.g., four, five, six, seven, eight, nine, ten, eleven, twelve, or soon) of sub-pixels.

FIG. 5 is a table illustrating examples of various patterns of pixelcluster arrangements. Specifically, column 502 shows a quarter pixelpattern in which pixel clusters 410 occupy a quarter of the area of thedisplay, in a regular array. In this example, the pixels have a densityof 222 pixels per inch. Transmissivity in this area is good (relative tothe other examples in the table), but image quality is poor.

Column 504 shows a diamond pixel pattern in which pixel clusters 412.Here, the clusters occupy 50% of the area. In this example, the pixeldensity is 313 pixels per inch, transmissivity of light through the areais moderate, while image quality provided by the display in this area isgood.

Column 506 shows a mosaic pixel pattern composed of pixel clusters 416with a pixel density of 313 pixels per inch. Transmissivity in this areais poor, and it provides moderate image quality.

Column 508 shows a stripe pixel pattern at 313 pixels per inch.Transmissivity of this area is moderate and image quality is good. Forall of these examples, the pixel density values shown in the drawing aremerely exemplary, and can be varied as desired.

FIG. 6 illustrates an example arrangement of pixel-clusters 302 in eachof the first area 204, the second area 206, the third area 208 and thefourth area 210 of display 202. Note that FIG. 6 shows a portion 600 ofthe display panel 202 shown in FIG. 2. Area 602 corresponding to aportion of the first area 204 which has one or more sensors 212underneath. Because of the sensors, electromagnetic radiation (e.g.,light) needs to pass through the OLED display 202 to the sensors 212 foroptimal (e.g., accurate) detection (e.g., sensing). Accordingly, ahighly transmissive pixel pattern is preferred for this area. In thisexample, area 602 has a quarter pixel pattern is shown which has goodlight transmission compared to the other patterns illustrated in FIG. 5.

Area 608 corresponding to a portion of the fourth area 210 of display202, which does not include sensors and corresponds to the largest areaof the display. Here, it is important that image quality is highest andtransmissivity is unimportant. Accordingly, in the present example, area608 includes maximum pixel density in which the pixel clusters arepacked as closely as possible.

To avoid or obviate the problem where the OLED display 202 has only twoareas, which can render a sharp undesirable contrast in image qualityalong the boundary of those two areas as described by FIGS. 1A and 1B,area 604 (corresponding to a portion of area 204 in display 202) andarea 606 (corresponding to a portion of area 206 in display 202) havepixel cluster patterns with intermediate pixel densities compared toareas 602 and area 608. In this example, area 604 includes a diamondpixel pattern and area 606 includes a mosaic pattern.

Because areas 206 and 208 are not adjacent to any front-facing sensors,the transmissivity of these areas is not important to the operation ofthe sensors. Accordingly, the reduced pixel density and correspondingpixel patterns can be implemented entirely in digitally. For example,image processing software in the device can program certain pixels inthese regions to remain inactive (i.e., black), thereby effectivelyproviding an area with reduced pixel density compared to the physicalpixel density of the display in that area.

To attain perceptual uniformity in brightness and color among differentareas 602, 604, 606 and 608, each of those panels can be calibratedrelative to each other. For example, the lower the resolution of pixels,the more the current can be provided to those pixels so that thedifferent pixel density areas have uniform brightness. The presence ofthree or more areas (e.g., four areas as shown in FIG. 2) with graduallychanging pixel-resolutions (as shown in FIG. 6) can therefore avoid theproblem of a sharp undesirable contrast in image quality along theboundary of two areas with significantly differing pixel-resolutions (asshown in FIGS. 1A and 1B).

Various implementations of the subject matter described herein (e.g.,the computing device 203, the display 202, and/or any other componentassociated with such computing device 203 and/or the display 202) can beimplemented in digital electronic circuitry, integrated circuitry,specially designed application specific integrated circuits (ASICs),computer hardware, firmware, software, and/or combinations thereof.These various implementations can be implemented in one or more computerprograms. These computer programs can be executable and/or interpretedon a programmable system. The programmable system can include at leastone programmable processor, which can have a special purpose or ageneral purpose. The at least one programmable processor can be coupledto a storage system, at least one input device, and at least one outputdevice. The at least one programmable processor can receive data andinstructions from, and can transmit data and instructions to, thestorage system, the at least one input device, and the at least oneoutput device.

These computer programs (also known as programs, software, softwareapplications or code) can include machine instructions for aprogrammable processor, and can be implemented in a high-levelprocedural and/or object-oriented programming language, and/or inassembly or machine language. As can be used herein, the term“machine-readable medium” can refer to any computer program product,apparatus and/or device (for example, magnetic discs, optical disks,memory, programmable logic devices (PLDs)) used to provide machineinstructions and/or data to a programmable processor, including amachine-readable medium that can receive machine instructions as amachine-readable signal. The term “machine-readable signal” can refer toany signal used to provide machine instructions and/or data to aprogrammable processor.

To provide for interaction with a user, the display 202 can display datato a user. The sensors 212 can receive data from the one or more usersand/or the ambient environment. The computing device 203 can thusoperate based on user or other feedback, which can include sensoryfeedback, such as visual feedback, auditory feedback, tactile feedback,and any other feedback. To provide for interaction with the user, otherdevices can also be provided, such as a keyboard, a mouse, a trackball,a joystick, and/or any other device. The input from the user can bereceived in any form, such as acoustic input, speech input, tactileinput, or any other input.

Although various implementations have been described above in detail,other modifications can be possible. For example, the logic flowsdescribed herein may not require the particular sequential orderdescribed to achieve desirable results. Other implementations are withinthe scope of the following claims.

1. An apparatus comprising: an organic light emitting diode (OLED)display comprising a first area having a first pixel density, a secondarea having a second pixel density, and a third area having a thirdpixel density, where the second area is arranged between the first areaand the third area and the first pixel density is lower than the secondpixel density, and the second pixel density is lower than the thirdpixel density; and a sensor arranged behind the OLED display andpositioned to detect electromagnetic radiation transmitted by the OLEDdisplay through only the first area of the OLED display, wherein each ofthe first, second, and third areas comprise a plurality of pixels, eachpixel of the plurality of pixels comprising one or more first sub-pixelsfor emitting light of a first color, wherein each pixel in the first,second and third areas has the same size and shape and the firstsub-pixels of the first, second, and third areas each have the same sizeand shape.
 2. The apparatus of claim 1, wherein the OLED display furthercomprises a fourth area between the second area and the third area, thefourth area having a pixel density between the second pixel density andthe third pixel density.
 3. The apparatus of claim 1, further comprisinga display driver module programmed to display images in the second areaat the second pixel density lower than a physical pixel density in thesecond area.
 4. The apparatus of claim 3, wherein the physical pixeldensity in the second area and a physical pixel density in the thirdarea are the same.
 5. The apparatus of claim 3, wherein the physicalpixel density in the third area and the third pixel density are thesame.
 6. The apparatus of claim 1, wherein pixels in the first area arearranged in pixel clusters in a first pattern and pixels in the secondarea are arranged in pixel clusters in a second pattern different fromthe first pattern.
 7. The apparatus of claim 6, wherein the firstpattern is a quarter pattern.
 8. The apparatus of claim 6, wherein thesecond pattern is a diamond pattern or a mosaic pattern.
 9. Theapparatus of claim 1, wherein the second area surrounds the first area.10. The apparatus of claim 9, wherein the third area surrounds thesecond area.
 11. The apparatus of claim 1, wherein the first area islocated at an edge of the display.
 12. The apparatus of claim 1, whereinthe first area is 10% or less of a total area of the OLED display. 13.The apparatus of claim 1, wherein the third area is 80% or more of atotal area of the OLED display.
 14. The apparatus of claim 1, whereinthe first pixel density is 250 pixels per inch or less.
 15. Theapparatus of claim 1, wherein the third pixel density is 400 pixels perinch or more.
 16. The apparatus of claim 1, wherein the sensor is acamera.
 17. The apparatus of claim 1, wherein the apparatus is asmartphone.